A World Meteorological Organization weather and climate extremes committee has judged that the world’s longest reported distance for a single lightning flash occurred with a horizontal distance of 321 km (199.5 mi) over Oklahoma in 2007, while the world’s longest reported duration for a single lightning flash is an event that lasted continuously for 7.74 s over southern France in 2012. In addition, the committee has unanimously recommended amendment of the AMS Glossary of Meteorology definition of lightning discharge as a “series of electrical processes taking place within 1 s” by removing the phrase “within 1 s” and replacing it with “continuously.” Validation of these new world extremes 1) demonstrates the recent and ongoing dramatic augmentations and improvements to regional lightning detection and measurement networks, 2) provides reinforcement regarding the dangers of lightning, and 3) provides new information for lightning engineering concerns.

A World Meteorological Organization (WMO) committee officially evaluated temperature record extremes of 54.0°C at two locations, one in Mitribah, Kuwait on July 21, 2016 and a second in Turbat, Pakistan on May 28, 2017. The committee agreed that quantity and quality of documentation of both observations were excellent. Additional metrological testing of the equipment focused on three aspects: the calibration of both thermometers, an effort to estimate the factors influencing the measurements and a direct comparison of the two thermometers when exposed simultaneously to 54°C. The metrological analysis's conclusion for the Mitribah value is a temperature estimated to be 53.87°C with an expanded uncertainty of ±0.08°C. Correspondingly, for the Turbat value the temperature is estimated to be 53.72°C with an expanded uncertainty of ±0.40°C. Following that analysis, the committee recommended acceptance of the calibrated observations to the first decimal digit such that the Mitribah observation is accepted as 53.9 ± 0.1°C and the Turbat as 53.7 ± 0.4°C. The Mitribah, Kuwait temperature is now accepted by the WMO as the highest temperature ever recorded for Asia (WMO RA II) and the two observations are the third (tied within uncertainty limits) and fourth highest WMO‐recognized temperature extremes and, significantly, they are the highest, officially recognized temperatures to have been recorded in the last 76 years. This evaluation has involved the most extensive temperature extremes analysis ever to be undertaken by an international evaluation committee of the WMO CCl Archive of Weather and Climate Extremes.

The record high temperature for regions south of 60°S latitude is a balmy 19.8°C (67.6°F), recorded 30 January 1982 at a research station on Signy Island.

This study explores long-term deviations from wind averages, specifically near the surface across central North America and adjoining oceans (258-508N, 608-1308W) for 1979-2012 (408 months) by utilizing the North American Regional Reanalysis 10-m wind climate datasets. Regions where periods of anomalous wind speeds were observed (i.e., 1 standard deviation below/above both the long-term mean annual and mean monthly wind speeds at each grid point) were identified. These two climatic extremes were classified as wind lulls (WLs; below) or wind blows (WBs; above

[1] Short-term tidal variations occurring every 27.3 days from southern (negative) to northern (positive) maximum lunar declinations (MLDs), and back to southern declination of the moon have been overlooked in weather studies. These short-term MLD variations' significance is that when lunar declination is greatest, tidal forces operating on the high latitudes of both hemispheres are maximized. We find that such tidal forces deform the high latitude Rossby longwaves. Using the NCEP/NCAR reanalysis data set, we identify that the 27.3 day MLD cycle's influence on circulation is greatest in the upper troposphere of both hemispheres' high latitudes. The effect is distinctly regional with high impact over central North America and the British Isles. Through this lunar variation, midlatitude weather forecasting for two-week forecast periods may be significantly improved.

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A World Meteorological Organization (WMO) committee evaluated the record sea-level pressure (SLP) measurement of 1089.4 hPa on 30 December 2004 in Tosontsengel, Mongolia (1724.6 m). Although instrumentation and data collection procedures were properly followed according to the assessment of the committee, concern was raised regarding the reliability of SLP adjustment from such a high-elevation station. This paper addresses this concern with a number of analyses that look at relationships between SLP extremes and corresponding station elevation and temperature. First, we selected data from stations extracted from the Integrated Surface Database (ISD-Lite) of NOAA's National Climate Data Center. A spatial analysis indicates that elevation shows little to no association (R 2 values essentially zero) to extreme SLP. However, a second analysis between extreme SLP and air temperature indicates that high regionalism exists in spatial correlations (local R 2 ) between those two variables. This relationship to temperature is likely the result of differences in SLP adjustment formulae used around the world. Based on this analysis, on the need to differentiate the SLP values adjusted using extremely cold temperatures (and generally high elevation), and following past WMO SLP guidelines, the WMO Rapporteurs for Climate and Weather Extremes therefore have created two distinct SLP records: (a) highest adjusted SLP (below 750 m), currently 1083.3 hPa recorded on 31 December 1968 at Agata, Evenhiyskiy, Russia; and (b) highest adjusted SLP (above 750 m), currently 1089.4 hPa (by Russian method; 1089.1 hPa by WMO formula) on 30 December 2004 in Tosontsengel, Mongolia. Future WMO guidance regarding SLP adjustment may lead to re-evaluation of this and other SLP records.

Thus, the findings of this research can assist in informing drought preparedness strategies to mitigate significant losses due to drought.